For in-oil applications, synchronous chain drive shoe tensioners are known comprising a leaf spring rotating about a fixed axis, and a guide shoe supported by the leaf spring and cooperating in contact with a chain. More specifically, the leaf spring comprises a first end portion hinged about the fixed axis, and a second end portion opposite the first and cooperating with a position-adjustable stop member, which pushes the guide shoe against the chain to tension the convex elastic member.
Shoe tensioners are not generally used in dry drives, such as conventional belt drives, on account of the severe wear and belt damage caused by friction of the shoe.
Synchronous drives have recently been designed comprising in-oil belts, in which known shoe tensioners have proved extremely sensitive to distortion of the belt, which is normally greater than that of a chain. Distortion may be caused, for example, by variations in operating temperature, and has been found to be poorly compensated by known shoe tensioners, thus resulting in widely varying tension of the belt, which impairs meshing conditions of the drive pulleys and results in anomalous operation of the drive.